@tomsoniq, others
You can add a datatype object into a "Reaction" layout but CHILD_DataType,TRUE is needed.
LAYOUT_AddChild,IDataTypes->NewDTObject(...,TAG_END),
CHILD_DataType,TRUE,
CHILD_NoDispose,TRUE,
I don't think a layout/window can display animations on its own, like others have said. You have to display frames one by one on your own.
Trying to display an anim gif as a datatype object that way (above) after installing gifanim datatype from os4depot simply crashes badly. In case the author of anim gif is interested it crashes with memory pointer DEADBEEF.